Production of seamless tubes



Jan. 20, 1-931. 5. ALVERMANN 1,789,721

PRODUCTION 0F SEAMLESS TUBES Filed March-s0. 1927 Patented Jan. 20, 1931 EWALD anvnnmmw, or

nussnnnonr, GERMANY I PRODUCTION OF SEAMLESS TUBES Application filed March 30, 1927, Serial N10. 179,612, andin Germany November 1, 1926.

My invention refers to the production of seamless metal tubes. It has for its primary object to provide means whereby such tubes can. be produced in a more perfect and less expensivemanner than was hitherto possible.

In the production of tubes from steel or wrought iron, more particularly in recent times, the various. methods of' producing seamless tubes have come more and more to the fore. The. efforts made on the world markets to replace welded tubes by seamless tubes have however up to the present been only partially successful, inasmuch as hitherto no one has succeeded in perfecting methods of production for more than certain sizes of seamless tubes. By far the larger proportion of the tubes made of wrought iron, that is, about 7 5 per cent. of

the world consumption, are produced welded,

and the only reason for the present day preference for welded tubes is that the production of seamless tubes is more expensive. This is due. to the high cost of the raw ma-.

5 'terial and to the unsatisfactory methods of manufacture. This is more particularly the case with the larger sizes of tubes, which in Germany are produced almost exclusively on the pilgering mill by Perrins process.

By this process a seamless hollow block is rolled out hot into a seamless tube in steps. This operation of rolling is known, and it may be divided into two simultaneous operations, in the first of which a part of the thick wall of the hollow or-tubular body is reduced in thickness or reduced by forging, and in the second of which this tube reduced by forging is smoothed in the second part of the roll calibre and reduced for 4 uniformity of dimensions. It is this second part of the rolling operation which requires tools that work with precision but that wear rapidly, and also machines on which the demands are severe and which involve a 4 high consumption of power. The final product of these two simultaneous operations is one which is secured only by the operators exercising the greatest care. The pilgering method has the further disadvantage that during the rolling operation the forward end of the blank is rolled out at higher temperatures than is its rearward end, the re? sult of which is that the final product is not uniform in quality. Notwithstanding that these 'pilgeringmills are provided with the best auxiliary devices and are-of exact construction, their output is yet very small and insuificient to enable-a seamless tube to bebproduced-which is as cheap as the welded tu e. I The purpose of the present invention is to remove the disadvantages hereinbefore described of the known method, or at least to diminish them very considerably.

-According to the present invention the rolling operation that is necessary to produce a seamless tube from a pierced bloom, billet or the like is divided and carried out by two separate rolling mills, that is to say, the first rolling'. mill does the '};Jr'eliminar y work of forging the bloom, billet or the like to produce a roughly forged intermediate blank of considerably greater wallthickness and smaller lengththan the tube to be produced, while the second rolling mill isprovided to convert this blank into the finished tube of predetermined greater length and smaller wall thickness, without, however, reducing the outer diameter. I

The first operation is carried out, in a pilgering mill, thesecond operation, in a double groove (two high) rolling mill (plug mill). After the completion of the pilgering the blank is cut up into a number of pieces or sections and these'sections, after being reheated, are converted into tubes in the double groove (two high) rolling mill by a being rolled over a stationary mandrel.

The process according to the present invention and a plant for carrying it out are illustrated diagrammatically in the accompanying drawings, in which a gig. 1 is a diagrammatic plan of the plant, an

Fig. 2 a diagram illustrating the hollow or tubular body and the product ofv the process in stages.

In the drawings, a is a pilgering mill as used inrolling blooms, billets and the like according to Perrins process, 6 a finishing rolling mill, a furnace, d a hot-iron saw. The hollow bloom 1 illustrated in the drawing is rolled out in the pilgering mill to produce a thick-walled roughly'forged intermediate 5 blank 2; the latter is then out up into sectionsv by the hot-iron saw d, and these sections, after passing through the furnace c are rolled out upon the double groove (two high) rolling mill 6 one after the other, by one or o more operations over a mandrel to produce the finished tube 3. The pilgering mill (1 produces. roughly forged thick-walled intermediate blanks in fairly large quantities, because the double groove (two high) rolling mill b' is in a position to take over the main art of the rolling work in finishing the hol-;

ow blanks 2 that have been cut up bythe hot-iron saw d and heated in the furnace 0, and is also able to convert these roughly forged sections into tubes having thin walls in one or more operations.

By the combination of apilgering mill and a double groove (two high) rolling mill a method of producing tubes is provided which zsdoes away with the disadvantages of the known rolling method described and emferent rolling process over a mandrel to convert same into tubes of predetermined greater length and smaller wall thickness than, but having substantially the same outer diameter as said roughl forged pieces.

3. The met 0d of producing seamless tubes comprising reducing the wall thickness of a hollow bloom by rolling on a pilgering mill to produce a roughly forged intermediate blank of materially greater wall thickness throughout and materially less length than the finished tubes, cutting said blank in two, reheating the roughlyforged out pieces and subjecting said pieces to a further rolling operation over a mandrel in a double groove (two-high) mill to convert same into tubes of redetermined greater length and smaller wal thickness than, but having substantially the same outer diameter as said roughly forged pieces. i In testimony whereof I aflix my signature.

' EWALD ALVERMANN.

bodies the advantages of the latter. Inasmuch as there is also an output which is several times as great as that of a pilgering mill, the cost of production of seamless tubes is, according to the invention, considerably re-' duced and there'is thus the possibility presented of the seamless products entering into better competition with welded tubes.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art. Y I

In the appended claims the term i bloom is intended to include billets and the like.

I claim j 1. The method of producing seamless tubes comprising reducing the wall thickness of a hollow bloom by rolling according tothe pilering process to producea roughly forged mtermediate blank of, materially greater wall thickness throughout and materially less" length than 1 the finished tubes, cutting said blank in two, reheating the. roughly forged out pieces and subjecting said pieces to a different rollin process to convert them into tubes of pre etermined greater len h and smaller wall thickness than, but having-substantial1ythe,same outer diameter-as said roughly forged pieces.

2. The method of producing seamless tubes comprising reducing the wallthickness of a hollow bloom by rolling according to the pilgering process to produce a roughly forged intermediate blank of materially greater wall thickness throughout and materially less length than the finished-tubes, cuttin said blank in two, reheating the roughly or ed "cut pieces and subjecting said pieces to a if- 

